Multiple sclerosis is associated with psoriasis. A case-control study.

Background: MS and psoriasis are both autoimmune diseases putatively mediated mainly by T cells.

Objective: We conducted a case control study to investigate whether patients with MS have a high rate of comorbid psoriasis.

Methods: The cohort consisted of 214 consecutive MS patients and a control group of 192 consecutive patients with headache.

Results: There was a higher than expected frequency of psoriasis among the MS patients. There was no gender effect and none of the 9 affected MS patients were among the 22 MS patients with primary progressive disease. Six of those 9 patients started interferon-β treatment after being diagnosed with MS, and 4 of them experienced exacerbation of psoriasis during exposure to interferon-β. There was no exacerbation in the co-morbid patients during treatment with other disease-modifying drugs.

Conclusions: Our observation confirms other reports on an association of MS with autoimmune diseases and supports the hypothesis of autoimmune pathogenesis for MS. The current findings should raise the level of awareness of psoriasis among patients with MS, and of the need to consider a potential exacerbation of psoriasis by interferon-β therapy.